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The major sourse of energy to power every inhabited or biosphered world is legitimatelly regarded to be the fusion power from the stars within the Main sequence. Even usually only sun-like stars are counted as p[ossible to have ecospheres or 'Goldilock zones'. Most often it is wrongly supposed that the stellar radiation caused by the hydrogen fusion in their cores should be used directly in non-processed, non-filtered, non-concentrated or non-deflected way.
Indeed as I many times quoted in previous posts in this forum ANY RADIATION sourse - from the brown dwarfs through the normal stars to the hot stellar corpses - white dwarfs, neutron stars and black holes; no matter of the distance between the sourse and the habitat or the wavelenght of the natural radiation could be utilized by solar lasers and/or mirrors to power with exact doses and quality ANY HABITAT - planet, supramundane shell or rotating space colony. That is about the EM-fusion power sourse...
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But enormous stockpile of ready energy -- the gravitational one - indeed the reason the stars to start burning and to keep on burning and caused by the force wich shapes the ultimate fate of the Universe -- is usualy neglected.
The gravitational energy is present mainly in three industrially accessible forms:
- the energy - kinetic and potential - of any ORBITING body;
- the energy of any body CONTRACTING under its own selfgravitation ( the 'geothermal' one );
- the energy of any ROTATING astronomical body;
For illustration the Sun radiates every second 3.99 x 10 E 26 J in 40% visible light, 50% IR, 9% UV and 1% x-ray, radio frequencies and other wavelenghts, caused by the turning of hydrogen in helium in its active core. That will persist another 5 billion years with big deviations in the total output per second and the Sun will become white dwarf. Say these 5 bln years are ~2x10 E 17 sec. and nowaday total output per secong is the average one. So, the nuclear fusion power reserve of the Sun is in the range of ~10 E 44 J for comparison with the further data. I just want to notice, also, that the stars from the G-class and all others from groups higher than , say M9 red dwarfs, are fast-burners and quite ineffective and dangerous fusion reactors -- which in LONG RUN - hundreds of millions or billions of years - imminently will KILL those who relly upon them without to interfere in their work! The same way as some planets ( Nercury, Venus...) should be sunshielded now and others artificially lit with concentrated or lasered light ( Mars, Gallileans, Saturn moons...) now - in order to be habitable, in the future Earth should be moved or sunscreened with parasol in order to be not overheated by the Sun which increases its luminocity with the age.
The Earth now receives 1.8x10 E 17 J/sec. or half a billionth of the total solar EM output or ~300 W / m2 effectivelly ( ~1.3 kW / m2 for perpendicular to the solar radiation surfaces ). From this enormous flux only 1.2x10 E 15 J are fixed by the plants of the earth`s biosphere per annum, which is dozens of times bigger than the mankind consumption per year and let accept this as a unit of measure for the power demands of an earth-sized habitat with nested in it mankind-sized human society with optimal economy and utilization of resourses... We see that now the mankind uses only miniscule part of the sollar EM power hitting the Earth...
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Than:
1. The energy confined in the axial rotation of the Sun is 2.7x 10 E 40 J -- it could provide us with all necessary energy for ~2.10 E 25 or ~ 20 trillion times to trillion years!!!
2. The axial rotational energy of , say , Uranus is 2.1 x 10 E 32 J -- effectivelly consumed it is enough for ~2x10 E 17 or two million trillion years of powering earth-sized habitat!!!
3. For the EARTH:
- first type of energy the orbiting body`s one - from de-orbiting the Moon we could gain 4x10 E 30 J !
- from de-spining the earth we could extract 1,6x10 E 29 J !
- the Earth`s geothermal energy stockpile measures 6x10 E 27 Joules !!!
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Hence as many times was pointed out ( by David Criswell, Paul Birch and many others) the mankinds longevity depends entirelly on the efficiency of the consumption of the natural sourses of energy. Asside the natural nuclear fusion in the stars, in the Universe there is enormous reserve of gravitational energy which we have to leaern how to use. After several trillions of years when all the stars stop shining -- than manipulation of the matter in gravitational mechanical manner will be the sourse of energy. Especially using the universal black hole gravity mills for mass transfornation of matter in energy and utilizing the rotational energy of the black holes.
Such way earth type of biosphere and civilization could live literrally indeffinitelly long in practical terms.
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Utilizing of the gravitational energy would be the conditio sine qua non est colonisation of the vicinities of sub-stellar ( brown dwarfs, free floating in the interstellar void planets - selfcollapsed out of a star system or ejected during the formation or thrown away by mass-loss of the central star becoming nova or supernova, or planets with too distant orbits from the fusor-central star...) or post-stellar ( white dwarfs, neutron and quark stars, black holes...) objects.
The solid matter around these non-fusors could be transformed in habitats - rotating space colonies, Burch`s supramundane shells, terraforming of the ready ~1 G or lower surface graviting planetary mass bodyes... which habitats to be powered/illuminated by the enormous reservoir of gravitational energy in the central non-star body - rotational, orbital and geothermal.
For example, see the first extrasolar planetary system found in the 1990`es. Around the pulsar PSR1257+12 orbit perhubs 4 planets ( http://www.daviddarling.info/encycloped … rplan.html ) : three of them are within the mass range of the terrestrial type and orbit closer than 1 AU to the pulsar and one is as big as Saturn and circles in Pluto-like orbit. The central neutron star rotates thousands times per second and also holds enormous amount of termal energy.
Having in mind the figures which I posted above in my previous post, than if a bunch of colonists decide to settle the system, they have everything necessary en situ: they may terraform the innermost three planets; AND build supramundane shell around the saturn-like one with surface area ~100 times bigger than Earth`s + terraform the eventual natural satelites of the last; AND they could shell-around the pulsar itself; AND they could use the system`s debris - planetoides, comets, dust - for construction materials for building of thousands times the earth area of open-air planetary sized or topopolis type of rotating space colonies --- --- everything provided with light and energy via orbital rings, lasers and mirrors from the vast reserves of the stellar corpse for trillions and trillions of years... without to take into account the possibilty to extract orbital energy via deorbiting of Oort cloud objects or other kind of matter moving within the gravitational sphere of influence of the pulsar.
A brown dwarf or even just a gas giant planet free floating in the interstellar space can host quite big earth-like civilization and biosphere rellying upon only its non-fusion energy reserves for timescales at least thousands of times longer than the 'glimpse' of the stellar stay in the Main sequence...
Gravity through rotation and supramundane shelling, indistinguishable from the earth`s illumination light supply, the basic design humans should feel themselves quite comfortable in such environments.
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Conserning the Interstellar planets, as well as these around post-stellar non-fusors or hawled on too distant orbits from the central star during the formation, as possible and plausible colonisation sites, excluding the non-round smaller cometary bodies, see:
http://www.gps.caltech.edu/faculty/stev … ...ets.pdf
and the pointed by Atitarev in other threads in this forum, Gerald Nordley`s article about the habitabilty of the smaller objects.
Even if the described in this article conditions didn`t develop or aren`t preserved naturally -- it is obvious that artificially by controlled methods of extracting the geotermal & axial rotational energy of such astronomical bodies -- earth-sized biospheres, respectivelly civilization ( or bigger ) could be sustained for trillions of years. I mean bodies with surface gravity lower than 1 G or up to several times higher. If the solid/liquid surface is not terraformable - than colonies in orbit or supramundane shells could be implemented. The mentioned surface air presures of 10 E 2 - 10 E 4 can be brethable as discussed for H/He atmosphere with traces of O2 ( but with the necessary partial presure of 0.15-0.4 bars ). If the 'surface' gravity at the chosen for habitation level is much higher than earth`s -- dozens of Gees -- than liquid breathing + full body imersion in this breathable ecosystem`s liquid could be utilized - but not highly probable, cause such Gees will need quite cooled brown dwarf, for which we luck sufficient timescales since the Big Bang. Even Moon size interstellar planets could offer splendid conditions for habitation and terraforming, the smallest planets with 1% of G surface gravity could at least be titan-formed with ~1bar of ~80 K N2 atmosphere entirelly on their geothermal reserves and ( latter ? ) rotational energy. If the planet roams as close as several light years to any star in Main sequence, than really huge soletas` mirrors/lenses deployed could concentrate the scattered available star-light from many sourses and provide earth-level of insolation on their surfaces -- if considered necessary by the colonists... The thrown away smaller bodies - comets and dust clouds could serve as sourses for from-scruch building of artficial planets and rotating colonies -- if someone decides it is usefull to establish grand scale civilization branches with such isolation and remotedness. If the interstellar planet is surrounded with some natural statelites or debris -- this will be of great use for the innitial steps of colonisation and planetary engineering -- as materials with huge orbital energy stockpile. If the interstellar planets are 'lonely' and all their mass is confined in their spheres -- they could be mined or other minor clumps of matter within the neigboring interstellar space to be used as sourses of building material and mechanical gravitational energy. AS many of these outcast gas-giant formation seeds will have big mag-fields ( say, these with at least earth`s mass or bigger ) innitially only electodynamical orbiting tethers will provide the incrementally growing colonies with first industrial, than biospherical power...
See,
http://www.space.com/scienceastronomy/p … 40720.html
Somewhere between the Saturn and Jupiter`s mass lies the upper boundary of the gravitational chemical redistribution within the planet`s body. The bottom line slowly vanishes with the lessening of the planet`s mass. The reason why the heavy objects have no distinct chemical distribution depth zones, may be is in the way of their formation, but rather in the supercritical state of all the matter due to the enormous pressures at their cores. From somewhere the jovian mass and up to infinity - the chemical elements distribution is rather evenly spread in the body`s volume, which gives greater opportunities from stellar or sib-stellar mining of the necessary compounds -- the same way as with our Sun, from which an advanced civilization could excavate jovian masses of non-H/He elements for colony construction works, via ram-scoops or orbital rings lifters...
Imagine objects from our Inner system ejected in the interstellar void. Lonely Earths, Marses, Moons, Sednas and Qwawars and Varunas, single and doble and multiple interstellar planets, free floating there big and little gas-giants with or without moon or ring systems... Single brown dwarfs mined for substances and de-rotated and/or de-heated to be sqeezed out their mechanical evergy... Artificial controlled coalescing of Oort clouds` or interstellary scattered cometary bodies or molecular clouds in planet-sized usable as real estates bodies... Intervening in the star-planetary fomation in order more low-mass efficiently and longer burning and calmer stars to emerge... Star-lifting of the present giant stars for more effective utilization of the matter/energy...
Export, say the Neptune system out to half a light year or several from any star -- the answer is that such sites offer anything needed for settlement and for sustaining the minimal measure-unit of one human civilization or bigger for trillions of years.
Even in the most classical scientific-concept frame and technology based only on the nowaday science, each bit of matter or bit of termodynamical gradient in the Universe could be made to serve as sourse for maintenance of common earth biosphere and nested within it - basic human design unit`s society.
At least small part of the mankind and the post-mankinds will keep the oldest human strategy of making environments fit to the present Human condition. Small part of practical infinity is also infinity...
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